CN110077015B

CN110077015B - Fillet filler and method for manufacturing fillet filler and composite structure

Info

Publication number: CN110077015B
Application number: CN201811577624.4A
Authority: CN
Inventors: A·罗西; W·M·阿什马维; S·阿普达尔哈伊姆; J·L·马可; M·R·马特森; A·W·巴特勒; A·W·布鲁姆; D·罗伊施
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 2014-02-04
Filing date: 2015-01-23
Publication date: 2021-08-10
Anticipated expiration: 2035-01-23
Also published as: US20180065314A1; CN110077015A; EP2902179A2; JP2015147411A; EP2902179A3; US9827710B2; CN104816493B; EP2902179B1; US10744722B2; JP6468813B2; CN104816493A; US20150217508A1

Abstract

The invention relates to a radius filler and a method for manufacturing the radius filler and a composite structure. The method of manufacturing the radius filler may include: providing a plurality of fibers; weaving the plurality of fibers into a woven preform; forming the woven preform into a woven radius filler; and cutting the braided radius filler to a desired length.

Description

Fillet filler and method for manufacturing fillet filler and composite structure

The invention is a divisional application of the Chinese patent application with the application number of 201510033838.5, the application date of 2015, 1 month and 23 days, and the invention name of fillet filler and a method for manufacturing the fillet filler and a composite structure.

Technical Field

The present disclosure relates generally to composite structures and, more particularly, to composite radius fillers (radius fillers) for composite structures and methods of making the same.

Background

Composite structures are used in a wide variety of applications due to their high strength to weight ratio, corrosion resistance, and other advantageous properties. In aircraft construction, composites are used in increments to form fuselages, wings, horizontal and vertical stabilizers, and other components. For example, a horizontal stabilizer for an aircraft may be formed from composite skin panels that are co-bonded or co-cured to an internal composite structure such as a composite stiffener or spar. The composite spar may extend from the bottom to the top of the horizontal stabilizer and be tapered in thickness generally in the spanwise direction to improve the stiffness characteristics of the horizontal stabilizer and reduce weight.

The composite stiffeners or spars may be provided in various cross-sectional shapes. For example, a composite stiffener or spar may be formed into an I-beam shape by bonding or curing two vertical webs of C-shaped composite channels together in a back-to-back arrangement. Each of the C-shaped channels may have horizontal flanges extending outwardly from the upper and lower ends of the web. Each horizontal flange may transition into the web in a radiused web flange transition. When the C-channels are joined back-to-back to form an I-beam stiffener, the radiused web flange transitions create longitudinal notches along the upper and lower ends of the I-beam stiffener. The longitudinal slot may be referred to as a radius filler zone or a strip of paste (nodle) zone. To improve the strength, stiffness and durability of the composite structure, the radius filler regions may be filled with a radius filler or paste strip formed from the composite material.

Unfortunately, existing radius fillers have a number of drawbacks that detract from their utility. For example, existing radius fillers exhibit cracking due to residual stresses that may occur during the manufacturing process (such as during cooling after curing). Residual stresses can occur due to thermal mismatch between the radius filler and the adjacent composite laminate surrounding the radius filler. In addition, certain radius fillers can result in sub-optimal pull-off strength at the bond between the stiffener and the skin panel under structural loading.

As can be appreciated, there is a need in the art for a radius filler that minimizes the occurrence of cracks during the composite manufacturing process and provides advantageous pull-off strength and that can be manufactured in a timely and cost-effective manner.

Disclosure of Invention

The above-mentioned needs associated with connecting composite components are specifically addressed by the present disclosure which provides a method of making a fillet filler or paste strip. The method may include providing a plurality of fibers and weaving the plurality of fibers into a woven preform. The method may further include forming the braided preform into braided radius filler and cutting the braided radius filler to a desired length. As described in more detail below, in some examples, the fibers may be reinforcing fibers (e.g., carbon fibers, glass fibers, carbon fibers,

Fibers, etc.). The matrix material may be a thermoset matrix material (e.g., an epoxy) or a thermoplastic matrix material (e.g., polyetherketoneketone, polyetheretherketone, etc.). In some examples, the fibers may include reinforcing fibers woven with thermoplastic fibers that melt when heated, impregnating the reinforcing fibers together, as described below. In other examples, the fibers may include only thermoplastic fibers that may be woven together and may be melted and impregnated together during the process of heating, forming, and stiffening the radius filler.

Additionally, a method of manufacturing a composite structure is disclosed. The method may include installing a woven radius filler in a radius filler region between opposing stiffener laminates. The method may additionally include assembling the base laminate with the stiffener laminate to encapsulate the woven radius filler within the radius filler region and form a laminate assembly. The method may further comprise curing the laminate assembly by applying heat to form the composite structure.

In other embodiments, a method of manufacturing a radius filler is disclosed. The method may include providing a radiused filler core and manufacturing a bushing. The method may additionally include covering the radius filler core with a liner to form a lined radius filler.

A method of manufacturing a composite structure is also disclosed. The method may include installing a bushed radius filler in a radius filler region between opposing stiffener laminates; assembling a base laminate with the stiffener laminate to encapsulate the lined radius filler within the radius filler region to form a laminate assembly. The method may further include curing the laminate assembly by applying heat to form a composite structure.

Also disclosed is a radius filler for installation in a radius filler zone of a laminate assembly. The radius filler may include a plurality of fibers encapsulated in a resin and woven into a braided radius filler. The braided radius fillers may have a generally triangular shape, i.e., having a concave radius filler side surface and a generally flat radius filler bottom surface.

A radius filler is also disclosed. The radius filler may include a radius filler core. The radius filler may additionally include a bushing covering the radius filler core. The lined radius filler may have a radius filler bottom surface and an opposing radius filler side surface. The rounded filler side surface may be concave. The rounded filler bottom surface may be substantially flat.

The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings below.

Drawings

These and other features of the present disclosure will become more apparent with reference to the accompanying drawings in which like reference numerals refer to like parts throughout, and in which:

FIG. 1 is a perspective view of an aircraft;

FIG. 2 is a perspective view of the horizontal stabilizer taken along line 2 of FIG. 1;

FIG. 3 is a perspective view of the composite reinforcement and radius filler taken along line 3 of FIG. 2 and illustrating the installation of the radius filler into the radius filler region of the composite reinforcement of FIG. 2;

FIG. 4 is a schematic taken along line 4 of FIG. 3 and illustrating a pull-off load acting on the interface between the stiffener laminate and the base laminate;

FIG. 5 is a perspective view of an embodiment of a woven radius filler;

FIG. 6 is a flow diagram illustrating one or more operations that may be included in a method of manufacturing a braided radius filler;

FIG. 7 is a schematic view of an embodiment of a manufacturing system for manufacturing a braided radius filler;

FIG. 8 is a perspective view of a woven preform having a cylindrical configuration;

FIG. 9 is a cross-sectional view of the woven preform taken along line 9 of FIG. 7;

FIG. 10 is a cross-sectional view of the first roller die set taken along line 10 of FIG. 7;

FIG. 11 is a cross-sectional view of the second roll mold set taken along line 11 of FIG. 7;

FIG. 12 is a sectional view of the third roller die set taken along line 12 of FIG. 7;

FIG. 13 is a schematic view of other embodiments of a manufacturing system for manufacturing braided radius fillers having a core manufacturing station for manufacturing a core upon which the braided radius fillers may be braided;

FIG. 14 is a schematic side view of a final forming station with separate upper and lower forming dies;

FIG. 15 is a schematic side view of the final forming station of FIG. 14 with the braided preform sandwiched between an upper forming die and a lower forming die for consolidating and/or curing the braided radius filler;

FIG. 16 is a cross-sectional view of the final forming station taken along line 16 of FIG. 14 and showing the upper and lower forming dies with adhesive fill ports and also showing an embodiment of a braided radius filler with an inner core;

FIG. 17 is a cross-sectional view of the final forming station taken along line 17 of FIG. 15 and illustrating the injection of adhesive into the adhesive fill port to form an adhesive tip (adhesive tip) on each fillet corner of the braided fillet;

FIG. 18 is a cross-sectional view of a braided radius filler having adhesive tips at each radius filler corner;

FIG. 19 is a perspective view of a woven preform with localized changes in the cross-sectional dimensions of the fibers due to changes in the offset angle of the fibers;

FIG. 20 is a side view of the woven preform of FIG. 19 and illustrates fibers formed at a first offset angle and a second offset angle (e.g., different offset angles) resulting in an area of localized variation in cross-sectional dimensions of the woven preform;

FIG. 21 is a perspective view of a woven radius filler in a final contour shape (contoured shape) having a localized reduction in cross-sectional dimension at locations corresponding to localized variations in cross-sectional dimension of the woven preform;

FIG. 22 is a perspective view of a radius filler woven during installation into a radius filler zone defined by a pair of stiffener laminates having local ply additions along a portion of the length of the stiffener laminate;

FIG. 23 is an exploded view of an embodiment of a woven radius filler wrapped with an adhesive layer;

FIG. 24 is a schematic view of other embodiments of a manufacturing system for manufacturing a braided radius filler and including a mandrel forming system downstream of a braiding station and further including a consolidation station and an inspection station;

FIG. 25 is a cross-sectional view of the mandrel forming system taken along line 25 of FIG. 24 and showing a movable mandrel die having a mandrel die cavity occupied by a braided radius filler;

FIG. 26 is a cross-sectional view of the mandrel formation system during injection of the ceramic matrix into the mandrel die cavity;

FIG. 27 is a cross-sectional view of a mandrel formation system with a ceramic matrix in a hardened state;

FIG. 28 is a schematic view of the manufacturing system of FIG. 24 with a mandrel forming system installed in the pressing system;

FIG. 29 is a cross-sectional view of the press system taken along line 29 of FIG. 28 and showing the mandrel formation system captured between the movable upper press and the press base of the press system;

FIG. 30 is a cross-sectional view showing the pressure application system separating the mandrel die from the mandrel forming base after consolidation of the braided radius filler;

FIG. 31 is a cross-sectional view of the mandrel formation system after dissolving and removing the hardened ceramic matrix in the mandrel mold cavity;

FIG. 32 is a schematic view of other embodiments of the manufacturing system of FIG. 28 and showing the mandrel formation system disengaged from the braiding station;

FIG. 33 is a cross-sectional view of the mandrel forming system showing dummy radius fillers (dummy radius fillers) temporarily installed in the mandrel die cavity;

FIG. 34 is a cross-sectional view showing the mandrel forming system injecting adhesive into the inside of the mandrel die cavity and around the virtual radius filler;

FIG. 35 is a cross-sectional view of a mandrel formation system with a ceramic matrix in a hardened state;

FIG. 36 is an exploded cross-sectional view of the mandrel forming system after removing the dummy fillet filler from the mandrel die cavity and showing the resulting profile shaped into a hardened ceramic matrix;

FIG. 37 is a flow diagram illustrating one or more operations that may be included in a method of assembling a radius filler with a composite laminate to form a composite structure;

FIG. 38 is a schematic side view of a pair of back-to-back stiffener laminates defining a radius filler region;

FIG. 39 is a schematic side view of a stiffener laminate and shows adhesive layers applied to an opposing pair of stiffener bullnose;

FIG. 40 is a schematic side view of an adhesive layer being wrapped onto the bottom surface of a radius filler;

FIG. 41 is a schematic side view of a base laminate being assembled to a stiffener laminate;

FIG. 42 is a schematic side view of a composite structure made by curing a laminate assembly containing woven radius filler wrapped with adhesive;

FIG. 43 is a flow chart illustrating one or more operations that may be included in a method of manufacturing a lined radius filler;

FIG. 44 is a perspective view of an embodiment of a radius filler core;

FIG. 45 is a perspective view of an embodiment of a braided sleeve;

FIG. 46 is a perspective view of a braided sleeve applied over a radius filler core to form a radius filler with a sleeve;

FIG. 47 is a cross-sectional view of a bushed radius filler installed within a radius filler region of a laminate assembly;

FIG. 48 is a perspective view of an embodiment of a radius filler with a bushing having a leg bushing formed from a woven material;

FIG. 49 is an exploded side view of a plurality of legs prior to connection to a radius filler corner of a main liner portion;

FIG. 50 is a schematic side view of an assembled liner radius filler with legs showing the knotted or stitched connection of the legs to the main liner portion;

FIG. 51 is a schematic side view of a legged bushing after weaving the legged bushing onto a cylindrically shaped virtual radius filler;

FIG. 52 is a schematic side view of a legged bushing woven over a triangular shaped virtual radius padding;

FIG. 53 is a schematic side view of an assembled legged bushing covering a radius filler core;

FIG. 54 is an exploded view of a legged bushing radius filler prior to assembly with a pair of back-to-back stiffener laminates and a base laminate;

FIG. 55 is a side view of the stiffener laminate, base laminate, and radius filler after assembly; and

figure 56 is a side view of an I-beam composite structure with upper and lower fillet fillers with vertical legs interconnecting the upper and lower fillet fillers.

Detailed Description

Referring now to the drawings, which illustrate various embodiments of the present disclosure, a perspective view of an aircraft 100 is shown in fig. 1, the aircraft 100 having a fuselage 102 extending from a forward end of the aircraft 100 to an aft end of the aircraft 100. The aft end may include a tail wing 110, the tail wing 110 having one or more tail surfaces for directional control of the aircraft 100, such as a vertical stabilizer 112 and a pair of horizontal stabilizers 114. The aircraft 100 may also include a pair of wings 108 extending outwardly from the fuselage 102 and one or more propulsion units 104. The fuselage 102, wings 108, vertical stabilizers 112, horizontal stabilizers 114, and/or other aircraft components may be formed into a composite structure 106.

Referring to FIG. 2, a partial cross-sectional view of a portion of the horizontal stabilizer 114 of the aircraft 100 of FIG. 1 is shown. The horizontal stabilizer 114 may extend from the stabilizer bottom to the stabilizer top in the outboard direction of the aircraft. As indicated above, the horizontal stabilizer 114 may be formed from a composite skin panel 150, and the composite skin panel 150 may be co-cured or co-bonded to one or more composite stiffeners 152 or spars. In fig. 2, composite stiffener 152 is shown as an I-beam 160, although composite stiffener 152 may be provided in various other cross-sectional shapes.

Referring to FIG. 3, a partially exploded view of the composite stiffener 152 of FIG. 2 is shown. The composite stiffener 152 may be constructed from a pair of C-channels 164 in back-to-back relationship to form an I-beam 160. Each C-channel 164 includes a web 166 having flanges 168 at the upper and lower ends of the C-channel 164. Each flange 168 transitions from the web 166 at a radiused web flange transition and results in the formation of a longitudinal radiused filler region 158 extending along the upper and lower portions of the I-beam 160. In one of the many embodiments disclosed herein, each of the upper and lower radius filler regions 158 may be filled with a strip of paste or radius filler.

In fig. 4, a schematic of a portion of the composite structure 106 is shown and a pull-off load 178 is shown acting on the interface between the stiffener laminate 162 and the base laminate 172. The pull-off load 178 is an out-of-plane load that may be transferred through the web 166 of the C-channel 164 to create a reaction force 180 on the opposite side of the woven radius filler 230. The pull-off load 178 and reaction force 180 may be oriented perpendicular to the plane of the base laminate 172 and tend to separate the flange 168 from the base laminate 172 or peel the flange 168 from the base laminate 172 and/or delaminate the composite layers making up the stiffener flange 168 and the base laminate 172. The pull-off load 178 may have a maximum magnitude at the location of the tangent point 156 of the flange 168 and the corresponding reinforcement bullnose 154.

In fig. 5, an embodiment of a braided radius filler 230 is shown in its final shape. The braided radius fillers 230 may be formed from continuous fibers 308 braided in multiple directions (instead of the uniaxial directions typical of conventional radius fillers). The multiple fiber orientation of the braided radius filler 230 may advantageously prevent or minimize the propagation of cracks in the composite surrounding the radius filler region 158. As indicated above, cracks in the radius filler may occur during the manufacture of the radius filler due to a mismatch in machining or residual strain due to processing (e.g., curing) operations. In this regard, residual strain in the fillet filler may result due to a mismatch in the coefficient of thermal expansion of the fillet filler relative to the coefficient of thermal expansion of the composite laminate surrounding the fillet filler. Advantageously, the braided fillet filler 230 as disclosed herein may provide increased crack cracking resistance and/or increased crack growth resistance. By reducing crack cracking or crack growth, composite stiffener 152 may exhibit improved pull-off load capacity relative to conventional composite stiffeners.

In fig. 5, the braided radius filler 230 may be formed from a plurality of composite reinforcing fibers 308. The fibers 308 may be dry fibers 324 that are woven by the knitting machine 304 and then wetted in the resin bath 330. Alternatively, the fibers 308 may be provided as prepreg fibers, which may be pre-impregnated or pre-coated with a resin, such as a thermoplastic resin or a thermosetting resin. Types of thermoplastic resins may include polypropylene, polyethylene terephthalate, polyetherketoneketone (i.e., PEKK), polyetheretherketone (i.e., PEEK), polyphenylene sulfide, polyetherimide (i.e., PEI), polyamide, and other types of thermoplastic resins. The type of thermosetting resin may include epoxy or other thermosetting resin composites. As indicated above, the fibers 308 are generally continuous along the length of the woven radius filler 230. In one embodiment, the fibers 308 may be formedIs a continuous composite tape 310 such as a single direction split film tape. The fibers 308 may include carbon fibers, aramid fibers, carbon fibers, aramid fibers, carbon fibers, aramid fibers, carbon fibers, aramid fibers, carbon fibers, aramid fibers, and carbon fibers,

Fibers, glass fibers or any other type of reinforcing fiber material or combination of these materials.

The braided radius filler 230 may be formed in a generally triangular shape with opposing concave radius filler side surfaces 232, and the braided radius filler may have a generally planar radius filler bottom surface 234. The radiused filler side surface 232 may be complementary in size and shape to the opposing stiffener bullnose 154 of the composite stiffener 152. In this regard, any of the fillet filler embodiments disclosed herein may be applied to stiffener shapes other than the I-beam 160 configuration. For example, any of the radius filler embodiments disclosed herein may be installed in the radius filler region 158 of any of hat section stiffeners, L stiffeners, Z stiffeners, and various other stiffener configurations. Further, the radius filler embodiments disclosed herein may be used to fabricate composite structures for any application, without limitation, and are not limited to use in composite aircraft structures such as the horizontal stabilizer 114 shown in fig. 2.

Referring to fig. 6, a flow diagram illustrating one or more operations that may be included in a method 500 of manufacturing a braided radius filler 230 is shown. Any of the steps (in whole or in part) of the method 500 may be performed using the manufacturing system 300 shown in fig. 7. Step 502 of method 500 may include: a plurality of fibers 308 are provided at the weaving station 302 of the manufacturing system 300. The fibers 308 may be disposed on a braiding spool 306 mounted on a creel of the braiding machine 304. The fibers 308 may be provided in any of a variety of different forms. For example, in an embodiment, the fibers 308 may be provided as pre-impregnated unidirectional split film tape that may be pre-impregnated with a thermoplastic resin as described above. However, in other embodiments, the fibers 308 may be provided as dry fibers 324, and the dry fibers 324 may be wetted in the resin bath 330 prior to weaving the woven preform 200 or after weaving the woven preform 200. As described in more detail below, for the dry fibers 324, the method may include heating the resin coating the dry fibers 324, at least partially curing the resin after forming, compacting, and/or incorporating the braided preform 200 into the braided radius filler 230 prior to installing the braided radius filler 230 in the radius filler region 158 of the composite reinforcement 152.

Fig. 7 illustrates an embodiment of a manufacturing system 300 for manufacturing a braided radius filler 230. Manufacturing system 300 may include any number of knitting machines 304. Each braiding machine 304 may include a plurality of braiding spools 306 containing dry fibers 324. The manufacturing system 300 may include a pulling mechanism 382 for continuously drawing the fibers 308 from the braiding spool 306 and assembling the braided fibers 308 with the braiding guide 312 to form the braided preform 200 in a biaxially braided configuration. Pulling mechanism 382 may pull woven preform 200 continuously through different stages of manufacturing system 300. Although not shown, braiding machine 304 may be configured to provide fibers 308 assembled as uniaxial fibers. The uniaxial fibers may be woven with the cross-woven fibers to form a triaxial woven configuration of the woven preform 200.

In some embodiments, the dry fibers 324 may pass through a set of supply rolls 328 and into a resin bath 330 located downstream of the braiding station 302, the resin bath 330 serving to coat the dry fibers 324 with resin. In other embodiments, the fibers 308 may be woven over the inner core 242 (see fig. 19), as described below. In other embodiments, resin bath 330 may be omitted and fibers 308 may be provided as pre-impregnated fibers 308 (such as composite tape 310) that are pre-impregnated with resin. For example, the composite tape may be provided as a pre-impregnated unidirectional tape such as a split film tape. The composite strip may be provided in any width (such as one-eighth inch, one-quarter inch), or in any other width. The fibers in the composite tape may be formed from any material including graphite or carbon, glass, ceramic, aramid, and any other type of reinforcing fiber material as noted above. In any of the examples disclosed herein, the fibers 308 may include a blend of reinforcing fibers and thermoplastic fibers. The reinforcing fibers may include high strength fibers such as the carbon fibers, graphite fibers, aramid fibers, and the like described above,

Fibers, fiberglass, and other reinforcing and/or high strength fibrous materials.

In some embodiments, reinforcing fibers may be combined or blended with thermoplastic fibers, such as by weaving the reinforcing fibers with the thermoplastic fibers as described above. In some examples, the reinforcing fibers may be combined with the thermoplastic fibers to form a core, and the reinforcing fibers and/or the thermoplastic fibers may be braided around the core. The thermoplastic fibers may be subjected to heat during the process of forming the radius filler. The heating of the thermoplastic fibers may at least partially melt the thermoplastic fibers and reduce their viscosity, allowing the melted thermoplastic material to infuse into the reinforcing fibers during the process of forming the radius filler. In other embodiments, the fibers 308 can be substantially all thermoplastic fibers woven together as disclosed herein. Heat may be applied to substantially all of the thermoplastic fibers, allowing the thermoplastic fibers to melt and melt together during the process of shaping and curing (e.g., hardening) the braided radius filler 230.

Step 504 of method 500 of fig. 6 may include braiding the plurality of fibers 308 into a braided preform 200 using one or more braiding machines 304. Although manufacturing system 300 in fig. 7 includes a single knitting machine 304, any number of knitting machines 304 may be provided. In some embodiments, braiding machine 304 may braid fibers 308 into a braiding barrel 202, as shown in fig. 8-9. In other embodiments, braiding machine 304 may be configured to braid fibers 308 into a braided preform 200, the braided preform 200 having a triangular cross-sectional shape with substantially straight sides (not shown). In other embodiments, the fibers 308 may be woven onto the inner core 242, as shown in fig. 16-19 and described in more detail below. The inner core 242 has a cross-sectional dimension smaller than the braided radius filler 230. The inner core 242 may be formed of the same material as the fibers 308 of the woven radius filler 230 or a different material. In some embodiments, the material of the inner core 242 may have a specific function. For example, the inner core 242 may be formed of a material that provides relatively high electrical conductivity. In other embodiments, the inner core 242 may be formed from a material that provides acoustic damping capability, impact resistance, or the inner core 242 may be formed from a material that can be used as a conduit for communication signals or data signals.

Step 506 of method 500 of FIG. 6 may include: the braided preform 200 is shaped and/or consolidated into the braided radius filler 230 by passing the braided preform 200 through a consolidation station 338. In the compaction station 338, the braided preform 200 may be formed into a generally triangular cross-sectional shape with concave rounded filler side surfaces 232 and a generally flat rounded filler bottom surface 234, as shown in fig. 12. In this regard, the compaction station 338 may include one or more forming dies for forming the braided preform 200. For example, fig. 7 shows a compaction station 338 that includes a series of roller sets for incrementally forming the woven cylinder 202 into a triangular shape with concave radiused filler side surfaces 232.

Fig. 10 illustrates initializing the braid 202 to form a rounded triangular cross-sectional shape by passing the braid 202 through a first roller die set 340. The first roller die set 340 may include a first upper die 342 and a first lower die 344, each of the first upper die 342 and the first lower die 344 being rotatable about a respective rotational axis. The first upper mold 342 may have a first mold cavity 346, the first mold cavity 346 having a first cross-sectional shape 348 with a triangular configuration. In some embodiments, the first roller die set 340 may be heated to allow the resin coating the fibers 308 of the woven preform 200 to be heated and softened to facilitate forming the woven preform 200. In other embodiments, the manufacturing system 300 may include one or more ovens 380 or other heating mechanisms for further heating and softening the resin to facilitate forming the braided preform 200. Although the oven 380 is shown disposed between the first roller die set 340 and the second roller die set 350, the oven 380 or other heating mechanism may be located anywhere along the manufacturing system 300. In some embodiments described below, the resistive wiring may be woven into the woven preform 200 to internally heat and soften the resin and woven preform 200, as described below.

In fig. 7, the braided preform 200 may be passed through a second roller mold set 350 having a second upper mold 352 and a second lower mold 354. Fig. 11 shows a cross-section of a second upper mold 352 having a second mold cavity 356, the second mold cavity 356 having a second cross-sectional shape 358 to shape the woven preform 200 closer to the final shape of the woven radius filler 230. The second roll mold set 350 may optionally be heated to facilitate softening the resin and shaping the braided preform 200. Fig. 12 shows a third roller die set 360 that may also be heated and may include a third upper die 362 and a third lower die 364. The third upper die 362 may include a third cross-sectional shape 368 for forming the concave radius filler side surface 232 and the generally flat radius filler bottom surface 234 of the braided radius filler 230. Although the manufacturing system 300 of fig. 7 illustrates a series of roller dies for shaping the woven preform 200 in a continuous moving process, the manufacturing system 300 may include one or more shaping dies of any size, shape, and configuration, without limitation. For example, the manufacturing system 300 may include one or more upper and lower clamp molds (not shown) or one or more stationary molds (not shown) with internal mold cavities for gradually shaping the fibers 308 into the final shape of the braided radius filler 230. In some embodiments, one or more of the forming dies may include provisions that may be used to form an adhesive tip 244 on the radius filler corner 236 to fill in the farthest corner of the cross-sectional shape of the radius filler region 158 of the composite stiffener 152. For example, fig. 17 shows an adhesive tip 244 that may be formed on the woven radius filler 230 by injecting adhesive into a corner of the mold cavity.

Step 508 of the method 500 of fig. 6 may include cutting the braided radius filler 230 to a desired length. In an embodiment, a cutting station (not shown) may be included downstream of the pulling mechanism 382. As indicated above, pulling mechanism 382 may be configured to pull fibers 308 from braiding station 302 and through compaction station 338 on a continuous basis. It is contemplated, however, that for a manufacturing system 300 having a vertically movable clamp die (not shown) for compacting and/or shaping the braided radius filler 230, the pulling mechanism 382 may be configured to operate on a pulsed feed basis (e.g., on a start-stop basis) for pulling the fibers 308 through various stages of the manufacturing system 300. The cutting station may be configured to cut the braided radius filler 230 to a length substantially equivalent to the length of the radius filler region 158, and the radius filler may be assembled in the radius filler region 158. In some cases, the braided radius fillers 230 may be cut to relatively long lengths, such as lengths of up to 50 feet or more for a single braided radius filler 230.

Referring to fig. 13, showing other embodiments of a manufacturing system 300 having a core manufacturing station 320 for manufacturing an inner core 242 (fig. 16), a braided radius filler 230 may be braided onto the inner core 242 (fig. 16). The inner core 242 may be formed from fibers 308 pulled from one or more core spools 322 using a pulling mechanism 382. The fibers 308 of the inner core 242 may be assembled at the core guide 326. In some embodiments, the inner core 242 may be formed in a generally cylindrical shape, although other shapes of the inner core 242 are contemplated. In some examples, the fibers 308 of the inner core 242 may be formed from the same material or different materials as the fibers 308 woven onto the inner core 242. In the illustrated embodiment, the fibers 308 may be provided as dry fibers 324, and the dry fibers 324 may pass through a set of supply rolls 328 and into a resin bath 330, the resin bath 330 being used to coat the dry fibers 324 with resin. However, the resin bath 330 may be omitted and the fibers 308 of the inner core 242 may be provided as pre-impregnated fibers 308 such as pre-impregnated composite tape 310. The fibers 308 may be braided over the inner core 242 to form a braided preform 200, such as a braided drum 202 (e.g., fig. 8). However, the inner core 242 may be provided in a non-cylindrical shape, such as a generally triangular cross-sectional shape or other shape, resulting in a correspondingly shaped braided preform (not shown).

In fig. 13, the pre-impregnated composite tape 310 of the woven preform 200 may be heated, such as by using one or more heated roller dies or an optional oven 380, to soften the resin and allow entanglement of the resin in the strands of the composite tape from which the woven preform 200 is made. The braided radius filler 230 may be allowed to cool and solidify after exiting the last roller die set of the compaction station 338. For thermosetting the prepreg tape, heat for curing the resin may be provided after the woven preform 200 is formed into a desired shape by a forming mold. In an alternative embodiment, the fibers 308 of the braiding machine 304 may be provided as dry fibers 324, the dry fibers 324 may pass through a resin bath 330, the resin bath 330 being used to wet the fibers similar to the wetting of the fibers at the core-making station 320.

Fig. 14 is an exploded side view of a final forming station 460 for consolidating and/or curing the braided radius filler 230 after the braided preform 200 is cut to a desired length after exiting the compaction station 338 shown in fig. 13. The final forming station 460 may include a forming die set 462 having an upper forming die 464 and a lower forming die 466. The forming die set 462 may be formed to have a length complementary to the length of the woven preform 200. The upper form die 464 is vertically movable to allow the braided radius filler 230 to be installed in the lower form die 466. The method of manufacturing the radius filler may include installing the braided radius filler 230 in a final forming die set 462, as shown in fig. 16. The braided radius filler 230 may optionally include an inner core 242. However, the braided radius filler 230 may be formed without the inner core 242.

In fig. 16, the lower forming die 466 may include a cavity having a contour that approximates the contour of the radius filler region 158 of the laminate assembly 176 (see, e.g., fig. 22), and the final radius filler may be installed as described below (fig. 22). As shown in fig. 15 and 17, the upper form 464 may cooperate with the lower form 466 to trap the woven radius filler 230 therebetween. In some embodiments, the braided radius filler 230 may be configured to cause intentional overfilling (interfacial over filling) of the braided radius filler 230 within the forming mold cavity such that, after curing, the braided radius filler 230 has a final volume that substantially matches the radius filler region 158. A method of manufacturing a radius filler may include applying heat and/or pressure 386 (fig. 15) to the woven radius filler 230 in a final forming die set 462 and forming the opposing radius filler side surface 232 into a final shape that is complementary to the contour of the radius filler region 158 (e.g., fig. 22) of the laminate assembly 176 in which the radius filler may be mounted.

In fig. 16-17, the forming die set 462 may optionally include one or more adhesive fill ports 468 for injecting adhesive into the cavity containing the woven radius filler 230 to form the adhesive tip 244 at the radius filler corner 236. The adhesive tip 244 may advantageously fill voids that may otherwise occur due to the inability of the woven fibers 308 to fit within the relatively narrow thickness of the endmost or tip of the radiused filler corner 236. In this regard, a method of manufacturing the woven radius filler 230 may include installing the woven radius filler 230 in a final form die set 462 as shown in fig. 16, and injecting an adhesive into the final form die set 462 as shown in fig. 17 to form an adhesive tip 244 on each radius filler corner 236 as shown in fig. 18. The adhesive tip 244 may be allowed to cool and cure with the resin in the composite layer, after which the braided radius filler 230 may be removed from the final forming die set 462.

Referring to fig. 19-20, an embodiment of a braided preform 200 is shown having a local variation 204 in the cross-sectional area or dimension of the braided preform 200. The localized variation 204 in the cross-sectional area or dimension of the braided preform 200 may contribute to the localized variation 238 in the cross-sectional area or dimension of the braided radius filler 230 as shown in fig. 21. In this regard, localized variations 238 may be formed in the braided radius filler 230 to accommodate the non-uniform profile in the radius filler region 158 of the composite structure 106. For example, one or both of the stiffener laminates 162 may include layer additions 184 or layer decrements 182 along the length of the stiffener laminate 162. Layer additions 184 may be included in the stiffener laminate 162 to locally increase the stiffener strength, such as to accommodate increased loading at that location or to accommodate mounting brackets or other hardware mounted to the stiffener at that location.

Referring briefly to fig. 13, a localized change 238 in the cross-sectional area of the braided radius filler 230 may be formed by adjusting the tension or pulling force 384 on the braided preform 200 as the fibers 308 are pulled from the braiding spool 306 and the fibers 308 are braided into the braiding guide 312. In this regard, a method of manufacturing the braided radius filler 230 may include varying the tension 384 on the braided preform 200 for different time intervals as the braided preform 200 is braided. In response to changing the tension 384, the offset angle of the fiber 308 can be changed. For example, by increasing the pulling force 384 on the fibers 308 being pulled through the braiding guide 312, the offset angle of the fibers 308 with respect to the longitudinal axis 206 may be increased from the relatively large first offset angle 208 of the braided preform 200 to the smaller second offset angle 210, as shown in fig. 20. A larger offset angle results in a larger cross-sectional dimension for the woven radius filler 230. A smaller offset angle results in a smaller cross-sectional dimension for the woven radius filler 230. The offset angle of the fibers 308 with respect to the longitudinal axis 206 may vary within any range (e.g., 10 to 80 degrees). The process of changing the offset angle of the fibers 308 results in changing the cross-sectional dimensions of the woven preform 200 as shown in fig. 19-20. In this regard, increasing the tension 384 on the braided preform 200 may decrease the cross-sectional area of the braided preform 200. Conversely, reducing the tension 384 on the braided preform 200 may increase the cross-sectional area of the braided preform 200.

By controlling the pulling mechanism 382 to adjust the pulling force 384 on the braided preform 200 as the braided preform 200 is pulled by the braiding guide 312, the length of the local variation 204 in cross-sectional dimension and position along the length of the braided preform 200 can be controlled. The local variation 204 in the cross-sectional dimension of the woven preform 200 may be formed to complement the local variation in profile along the length of the radius filler region 158 (see, e.g., fig. 22). In this regard, the cavity in the lower forming die 466 (see, e.g., fig. 16) may be contoured along the length in a manner that substantially replicates the contour along the length of the radius filler region 158 of the laminate assembly 176 (fig. 22). In some embodiments, the offset angle may be varied to achieve a desired stiffness or carrying capacity of the braided radius filler 230.

In fig. 23, an exploded illustration of the braided radius filler 230 wrapped around the adhesive is shown prior to assembly of the braided radius filler 230 with the stiffener laminate 162 and the base laminate 172. In some examples, the adhesive layer 240 may be applied to the fillet side surface 232 and the fillet bottom surface 234 prior to installing the adhesive-wrapped braided fillet 230 in the fillet region 158. In other examples, the adhesive layer 240 may be applied to the surface of the opposing stiffener bullnose 154 prior to installing the braided radius filler 230 in the radius filler region 158, as described in more detail below and shown in fig. 39. Prior to mounting the base laminate 172 onto the woven radius filler 230, the radius filler bottom surface 234 may be over-wrapped with an adhesive layer 240, as shown in fig. 40. Advantageously, the adhesive wrapped braided radius filler 230 may improve toughness, durability, and crack resistance at the boundaries of the braided radius filler 230 and the stiffener laminate 162 and base laminate 172. As described in more detail below, the stiffener laminate 162 may also be provided with relatively large fillets to improve stress distribution at the boundary between the rounded filler side surface 232 and the stiffener bullnose 154, thereby increasing the pull-off strength of the stiffener laminate 162 relative to the base laminate 172. Any of the manufacturing systems 300 and methods described herein may be used to manufacture the adhesive-wrapped braided radius filler 230.

Figure 24 illustrates an embodiment of a manufacturing system 300 that uses a mandrel forming station 420 located downstream from the braiding station 302 to consolidate and/or cure the braided radius filler 230. Manufacturing system 300 may include a knitting station 302, knitting station 302 having one or more knitting machines 304 similar to the knitting machines described above. The pulling mechanism 382 may pull the braided preform 200 through the braiding guide 312. The mandrel forming station 420 may include a mandrel forming system 422 for forming the braided preform 200 into the desired final shape of the braided radius filler 230. The manufacturing system 300 may operate in a pulsed flow mode, wherein a continuous length of the braided preform 200 may be shaped, consolidated, and/or cured using the mandrel forming system 422 in conjunction with the pressure application system 400.

Referring to FIG. 25, the mandrel forming system 422 may include a mandrel die 424 and a mandrel forming base 426 that may cooperate with one another. The mandrel die 424 may include a mandrel die cavity 428, and the mandrel die cavity 428 may be sized and configured to receive the braided preform 200 and provide additional space between the mandrel die cavity 428 and the surface of the braided preform 200. In the illustrated embodiment, the braided preform 200 may be braided into a triangular cross-sectional shape that may approximate the final shape of the braided radius filler 230, although the braided preform 200 may be braided into other cross-sectional shapes. Although not shown, the woven preform 200 may optionally include an inner core 242 as described above. In other embodiments, the braided preform 200 may include one or more internal heating wires 246, such as resistance wires. The heating wire 246 may be wound onto one or more braiding spools 306 of one or more braiding machines 304, causing the heating wire 246 to be braided internally into the braided preform 200.

Although fig. 25 shows three (3) heating wires 246 woven internally into the woven preform 200, any number of heating wires may be included. The heater 246 may be arranged in the woven preform 200 in any manner and is not limited to the triangular shape arrangement of the heating wire 246 shown in the figures. For example, the heating filaments 246 may be woven such that some of the heating filaments 246 are disposed adjacent to one or more surfaces of the woven preform 200, or the heating filaments 246 may be disposed inside and on or beside one or more surfaces of the woven preform 200. In an embodiment, the heating wire 246 may be resistively heated by passing a current through the heating wire 246. The heating wire 246 may be used to heat 388 and soften the resin coating the pre-impregnated fibers 308 of the woven preform 200 to allow the woven radius filler 230 to be cured, and/or hardened. The heating wire 246 may soften the resin prior to and/or during consolidation of the braided radius filler 230 contained within the mandrel formation system 422. The heating wire 246 may also assist in heating the expandable ceramic matrix 432 (see, e.g., fig. 26), causing it to expand when the mandrel forming system 422 is clamped within the pressing system 400, as described in more detail below.

Fig. 26 illustrates the injection of an expandable dissolvable ceramic matrix 432 into one or more fill ports 430 in the mandrel die 424 of the mandrel forming system 422. The ceramic matrix 432 may be provided as a slurry or semi-liquid composition. The infused ceramic matrix 432 may fill the volume of the space between the braided radiused filler side surface 232 and the walls of the mandrel die cavity 428. The ceramic matrix 432 may be continuously introduced into one of the ports 430 until the excess ceramic matrix 432 begins to flow out of the other port. Fig. 27 shows the ceramic matrix 432 in a hardened state, after which the port 430 may be closed with a plug 434.

Figure 28 shows the mandrel forming system 422 clamped over the braided radius filler 230 and moved into the compression system 400. The mandrel die 424 and mandrel forming base 426 may be clamped within a pressing system 400 located between the movable upper press 402 and the pressing base 404, as shown in FIG. 29. The press system 400 may include an actuator 406, such as a mechanical or hydraulic actuator, for vertically moving the movable upper press 402 relative to the press base 404 between an open position (fig. 24 and 30) and a closed position (fig. 28-29). Clamping the mandrel forming system 422 within the pressing system 400 (fig. 29) prevents relative movement of the mandrel die 424 during expansion of the ceramic matrix 432 as the ceramic matrix is heated. Heat may be applied to mandrel forming system 422 in a conventional manner, such as by placing pressing system 400 in autoclave or oven 380. Alternatively, the mandrel forming system 422 may be integrally heated to help heat the expandable ceramic matrix 432 and cause it to expand and consolidate the braided preform 200 as the mandrel forming system 422 is clamped between the movable upper press 402 and the pressing substrate 404. For example, in an embodiment not shown, the movable upper press 402 and press base 404 may include an upper base facesheet (not shown) and/or a lower base facesheet (not shown), respectively, that may be positioned to contact the mandrel die 424 and the mandrel forming base 426, respectively. The upper and/or lower base facesheets may be inductively heated in response to alternating current, which may pass through one or more induction coils (not shown) that extend through the movable upper press 402 and/or the press base 404. A background example OF this arrangement can be found in U.S. application Ser. No. 13/305,297 entitled "SYSTEM AND METHOD OF ADJUSTING THE EQUILIBRIUM TEMPERATURE OF AN INDUCTIVELY-HEAT SUSCEPTOR", filed on 28.11.2011.

As disclosed in serial No. 13/305,297, the upper and/or lower base face sheets may be formed from an electrically conductive ferromagnetic alloy having a Curie temperature (Curie temperature) that depends on the composition of the ferromagnetic alloy. In this regard, the ferromagnetic alloy forming the upper and/or lower base face sheets may be selected based on the desired temperature to which the expandable ceramic matrix 432 may be heated. For example, a ferromagnetic alloy composition having a curie temperature may be selected to result in an equilibrium temperature of the upper and/or lower base face sheets that generally corresponds to the temperature at which the ceramic matrix 432 expands in a manner that causes the braided radius filler 230 to consolidate within the mandrel forming system 422. In other embodiments, the ferromagnetic alloy composition of the upper and lower base facesheets may be selected based on the processing temperature of the resin (e.g., glass transition temperature or melting temperature of the thermoplastic resin; curing temperature of the thermosetting resin, etc.) contained in the braided radius filler 230 trapped within the mandrel die cavity 428. Advantageously, by using an inductive susceptor system having upper and/or lower susceptor face sheets, the time associated with heating the mandrel forming system 422 and the ceramic matrix 432 and/or the resin contained in the pre-impregnated fibers 308 may be significantly reduced relative to the substantial time required to heat the mandrel forming system 422 using conventional heating techniques such as autoclaves or ovens (due to the large heat associated with autoclaves and ovens).

Fig. 29-31 illustrate a method of manufacturing a braided preform 200 by installing the braided preform 200 in a mandrel forming system 422 and injecting a ceramic matrix 432 into a mandrel mold cavity 428 containing the braided preform 200. The method may include heating the resin of the fibers 308 to a temperature that causes the resin to soften. Additionally, the method may include heating 388 (fig. 29) the ceramic substrate 432 in a manner that causes the ceramic substrate 432 to expand when the mandrel forming system 422 is clamped within the pressing system 400. The method may further include consolidating the braided radius filler 230 in response to expansion of the ceramic matrix 432 and allowing the resin to cool and harden, after which the braided radius filler 230 may be inspected at an inspection station 450 located downstream of the pressing system 400. The inspection may be configured to inspect for defects in the consolidated or compacted radius filler, such as voids, air holes, or other defects. In some embodiments, the inspection station may include a non-destructive inspection apparatus, such as a transmission ultrasound inspection apparatus.

In fig. 31, the mandrel forming system 422 may be reused after consolidating the braided radius filler 230 by separating the mandrel die 424 from the mandrel forming base 426, removing the braided radius filler 230, and applying a solvent to the stiffening matrix 436 to remove the stiffening matrix 436. For example, water may be sprayed onto the solidification matrix 436 to dissolve the solidification matrix 436 and allow the solidification matrix 436 to be removed from the mandrel die cavity 428 so that the mandrel forming system 422 may be used for another section of braided radius filler 230.

In an embodiment (see, e.g., fig. 32), the mandrel forming station 420 may be disposed off-line and/or physically separate from the braiding station 302 and the inspection station 450. In this regard, mandrel forming station 420 may be disposed at a location separate from braiding station 302 and may utilize dummy radius fillers 438 to form ceramic matrix 432 into a dissolvable mandrel, which may then be disposed throughout the length of braided radius fillers 230 and clamped within pressure application system 400. Fig. 33 shows a cross-section of a mandrel formation system 422 that may be mounted on a movable table or other support. The dummy radius filler 438 may have a shape or profile that may match the shape or profile of the radius filler region 158, into which the radius filler may be installed, as shown in fig. 22 and described above.

Fig. 34 shows a ceramic matrix 432 being injected into the sprue 430 to fill the space between the side surfaces of the dummy fillet fill 438 and the surface of the mandrel die cavity 428. Fig. 35 shows a ceramic matrix 432, such as hardened at room temperature. After the ceramic matrix 432 has hardened, the port 430 may be closed with a plug 434 similar to the plug described above and a dummy radius filler 438 may be removed from the mandrel formation system 422. Next, the mandrel forming system 422 may be installed in the pressing system 400. Fig. 36 shows the mandrel die 424 separated from the mandrel forming base 426 to allow the mandrel forming system 422 to be clamped within the length of the braided radius filler 230, as shown in fig. 29. Heating 388 the hardened ceramic matrix 432 to cause it to expand and consolidate the braided radius filler 230 (fig. 29) may be performed as described above. After consolidating the braided radius filler 230, the mandrel die 424 may be separated from the mandrel formation base 426 and the stiffening matrix 436 may be dissolved using a solvent (e.g., water) and removed from the mandrel die 424 as shown in fig. 31 to allow the mandrel formation system 422 to be reused over another length of the braided preform 200.

Figure 37 is a flow diagram illustrating one or more operations that may be included in a method 600 of installing a braided radius filler 230 in a radius filler zone 158 of a composite structure 106. The method 600 is schematically illustrated in fig. 38-42. The method 600 may include applying an adhesive layer 240, such as an adhesive sheet, to the surface of the opposing stiffener bullnose 154. The stiffener bullnose 154 is part of a pair of back-to-back stiffener laminates 162. The stiffener laminate 162 may be provided back-to-back C-channels 164, L-segments, or other shapes that create a rounded filler region 158. As shown in fig. 39, the adhesive layer 240 may extend from the tangent point 156 of the horizontal portion of the flange 168 and be applied to the common tangent point 156 between the webs 166 inside the radius filler region 158. Next, the adhesive layer 240 may be applied over the opposing stiffener bullnose 154 with an excess portion of the adhesive layer 240 extending beyond the tangent point 156. Step 602 of method 600 may include mounting the braided radius filler 230 onto the adhesive layer 240 as shown in fig. 40 such that the radius filler side surface 232 contacts the adhesive layer 240. Fig. 40 additionally shows overcladding of the rounded filler bottom surface 234 with an adhesive layer 240.

Step 604 of the method 600 of fig. 37 may include assembling the base laminate 172 with the stiffener laminate 162 to encapsulate the woven radius filler 230 within the radius filler region 158 and form the laminate assembly 176, as shown in fig. 41. The base laminate 172 may be mounted on the flange 168 of the stiffener laminate 162 such that the base laminate engagement surface 174 contacts the flange engagement surface 170. Ideally, the adhesive layer 240 and the woven radius filler 230 are sized and shaped to completely fill the radius filler region 158 defined by the stiffener bullnose 154 and the lower surface of the base laminate 172. Step 606 of the method 600 may include curing the laminate assembly 176 (fig. 42) by applying heat and/or pressure to form the composite structure 106. For example, the laminate assembly 176 may be vacuum bagged and placed within an autoclave to co-cure and/or co-bond the stiffener laminate 162 with the base laminate 172.

Referring to FIG. 43, a flow diagram of one or more operations that may be included in a method 700 of manufacturing the lined radius filler 260 is shown. Step 702 of the method may include providing a radiused filler core 266 as shown in fig. 44. In some embodiments, the radius filler core 266 may be sized, shaped, and/or configured to substantially match the radius filler region 158 of the composite laminate that may be assembled with the gasketed radius filler 260 (e.g., fig. 3 and 22). In some examples, the radius filler core 266 may be a non-woven core and may be formed from fibers 308 such as thermoplastic or thermoset pre-impregnated unidirectional tape that may be stacked or laminated. The fibers 308 of the rounded filler core 266 may be similar to the fibers 308 of the liner.

In some examples, the rounded filler core 266 may include chopped or short fibers embedded within a thermoplastic or thermoset resin matrix. Advantageously, the chopped or short fibers may be oriented in various directions that minimize the coefficient of thermal expansion of the radius filler in the transverse direction (e.g., perpendicular to the long axis), thereby reducing thermal shrinkage in the transverse direction during cooling after curing or hardening the radius filler. In this regard, the shrinkage of the radius filler core 266 formed from chopped or chopped fibers may be reduced relative to the amount of shrinkage that may occur in conventional radius fillers having axial fibers extending along the length of the conventional radius filler. Advantageously, the reduced shrinkage in the cross direction results in reduced interlaminar stresses at the interface between the radiused filler side surface 232 and the reinforcement laminate 162, thereby reducing the tendency for cracking to occur. In some embodiments, the rounded filler core 266 of a triangular cross-sectional shape may be formed from short or chopped fibers by extruding, casting, or rolling the rounded filler core 266 into a desired shape. In other embodiments, the rounded filler core 266 may be formed from foam, metal or non-metal tubes or rods, or other materials. The metallic material of the radius filler core 266 may include titanium, aluminum, steel, or other alloys. The non-metallic material of the radius filler core 266 may include ceramic materials and polymeric materials.

In some embodiments, the rounded filler cores 266 may be formed of a material having a particular function other than the rounded filler cores 266, thereby helping to transfer loads between the base laminate 172 and the stiffener laminate 162. For example, the fillet filler core 266 may be formed of a conductive material that is used for conductivity, such as dissipating static charge buildup within the composite structure 106. In other embodiments, the rounded filler core 266 may be formed from a material that serves as a conduit for communication or data transfer. In other embodiments, the rounded filler core 266 may be selected from materials that provide acoustic damping to the composite structure 106 as indicated above.

Step 704 of the method 700 of fig. 43 may include fabricating a bushing for the bushed radius filler 260. In some embodiments, the liner may be manufactured as a hollow braided tube 264 having a cylindrical shape as shown in fig. 45. In other embodiments, the bushings may be woven in a hollow triangular shape (not shown) that may approximate the shape of the rounded filler core 266. As indicated above, the fibers 308 of the braided liner 262 may be formed of the same material as the fibers 308 of the rounded filler core 266.

Step 706 of the method 700 of fig. 43 may include covering the radius filler core 266 with a liner to form a lined radius filler 260 as shown in fig. 46. For example, some embodiments may include braided fibers 308 on a radius filler core 266 to form a braided sleeve 262 covering the radius filler core 266. The assembled radius filler and bushing may be cured and/or solidified to form a bushed radius filler 260. Other embodiments may include woven fibers 308 on the dummy radius fillers 438. For example, the dummy radius filler 438 may be formed from any suitable material, including but not limited to a foam core, an expandable core, a dissolvable core, or another removable core. After forming the liner, the method may include removing the dummy radius filler 438 from the braided liner 262, and then pulling the braided liner 262 onto the radius filler core 266. Next, the lined radius filler 260 may be installed in the radius filler region 158 to form a laminate assembly 176 similar to the laminate assembly shown in fig. 47.

In some embodiments, the method may include manufacturing the sleeve as a legged sleeve 270 as shown in fig. 48. The legged bushing 270 may have at least one leg 274 extending outwardly from the main bushing portion 272. The leg 274 of the legged spacer 270 may extend along the length of the main spacer portion 272. The leg-strap bushing 270 may be configured such that one or more legs 274 intersect the main bushing portion 272 at one or more filleted filler corners 236 of the filleted filler. In some embodiments, the legged spacer 270 may be formed in a generally triangular cross-sectional shape similar to the shape of the rounded filler core 266.

Fig. 48 shows a bushing with three legs 274 extending outwardly from each of the three radius filler corners 236. The legged spacer 270 may be configured such that at least one of the legs 274 has a leg width 276, the leg width 276 being at least as wide as the rounded filler bottom surface 234 and/or the rounded filler side surface 232. However, the leg 274 may be provided in any width 276 without limitation. Further, the legged spacers 270 may be provided in an asymmetrical configuration, wherein one of the legs 274 may be less wide than one or both of the remaining legs 274. In some embodiments, a method of manufacturing a liner may include weaving the fibers 308 into a legged liner 270, wherein the leg 274 and the main liner portion 272 are woven into a unitary structure 288 (not shown). In this regard, the legged spacer 270 may be configured such that the juncture 284 of each leg 274 with the main spacer portion 272 is seamless.

In other embodiments, the method may include assembling the bushing from the woven material 280 to form a woven bushing 278. For example, fig. 48-50 illustrate a legged spacer 270 formed from a woven material 280. A method of manufacturing a leg strap bushing 270 may include connecting at least one leg 274 to a main bushing portion 272 along a bushing length using through-thickness stitching 282. Full-thickness stitching 282 may be installed along fillet filler corner 236 of main liner portion 272, as shown in FIG. 48. In this regard, fig. 48 illustrates an assembled legged bushing 270 covering a radius filler core 266 and illustrates full thickness stitching 282 connecting each leg 274 to the main bushing portion 272 at each radius filler corner 236. Advantageously, the full thickness stitching 282 at the radius filler corner 236 may reduce or prevent delamination at the radius filler corner 236 of the assembled composite structure 106.

Fig. 51 shows a legged spacer 270 woven around a virtual radius filler 438 having a cylindrical cross-sectional shape. The braided liner 262 includes a main liner portion 272 and three leg portions 274 extending outwardly from the main liner portion 272 and formed integrally with the main liner portion 272. In this regard, the braided sleeve 262 is formed as a unitary structure 288. The legs 274 are connected to the main liner portion 272 in a position such that when the liner is pulled up over the radius filler core 266, the juncture 284 of each leg 274 to the main liner portion 272 is at one of the corners of the radius filler core 266 as shown in FIG. 53.

Fig. 52 shows a legged spacer 270 woven over a virtual radius filler 438 having a triangular cross-sectional shape. The virtual radius filler 438 is sized and configured such that the juncture 284 of the leg 274 with the main liner portion 272 coincides with the location of the radius filler corner 236, as shown in fig. 53. Figure 53 illustrates a lined radius filler having a leg liner mounted on a radius filler core 266. Legged spacer 270 may be formed as a braided spacer 262.

Figure 54 is an exploded view of the bushed radius filler 260 assembled with a pair of stiffener laminates 162 and base laminate 172. Each leg 274 of the padded radius filler 260 may connect with the main liner portion 272 at a junction 286 at the corner of the radius filler. In an embodiment, each node 286 may include a through-thickness stitch 282 or other attachment mechanism for attaching leg portion 274 to main liner portion 272.

Fig. 55 shows the assembled stiffener laminate 162 and base laminate 172 with the bushed radius filler 260 captured therebetween. The through-thickness stitches 282 in the bushed radius filler 260 coincide with the tangent points 156 of the flanges 168 on each stiffener laminate 162. Ideally, the full thickness stitching 282 has a minimum thickness to allow the flange engagement surface 170 to be disposed adjacent the engagement surface 174 of the contact base laminate 172 for bonding the laminates together during co-curing or co-consolidation of the laminates.

FIG. 56 illustrates other embodiments of the composite structure 106 in which the vertical leg 274 of the lower radius filler is identical to the vertical leg 274 of the upper radius filler. The interconnection of the lower fillet filler and the upper fillet filler may increase the pull-off load 178 capability of the composite stiffener 152. In addition, fig. 56 shows that the horizontal leg 274 of the lower radius filler is longer than the horizontal leg 274 of the upper radius filler. The increased length of the horizontal legs 274 of the lower radius filler may improve the pull-off load 178 of the lower flange 168 and the lower base laminate 172. It should be noted that the leg-carrying radius filler may not necessarily be provided with the symmetrical leg 274. For example, the leg 274 on one side of the radius filler may be longer than the leg 274 on the opposite side of the radius filler.

Advantageously, the radius filler having leg-bearing spacers 270 may reduce the tendency for delamination or debonding at the interface between the radius filler and the laminate sheet. In this regard, the radius filler having the legged bushings 274 may act as a framework to interconnect the laminates and thus may reduce stress at the radius filler regions 158 at the radius filler corners 236. In addition, the radius filler with the legged bushings 270 may spread or distribute the load so that it is transferred between the web 166 and the flange 168 of the stiffener laminate 162. In this regard, the legged spacer 270 may prevent localized stress concentrations in the radius filler region 158. In addition, the legged spacer 270 may accommodate thermal expansion mismatch between the radius filler region 158 and adjacent laminates, such as during shrinkage after curing or consolidation of the load laminates making up the composite structure 106.

Additionally, the present disclosure includes embodiments according to the following clauses:

1. a method of manufacturing a radius filler, the method comprising the steps of:

providing a plurality of fibers;

weaving the plurality of fibers into a woven preform;

forming the woven preform into a woven radius filler; and

cutting the braided radius filler to a desired length.

2. The method of clause 1, wherein the step of shaping the woven preform comprises:

forming the braided radius filler into a generally triangular cross-sectional shape having a rounded filler bottom surface and opposing rounded filler side surfaces, the rounded filler side surfaces each being concave, the rounded filler bottom surface being generally flat.

3. The method of clause 1, wherein the plurality of fibers are provided as a pre-impregnated composite tape containing resin, the step of shaping the woven preform comprising:

heating said pre-impregnated composite tape of said woven preform;

softening and entangling the resin in the pre-impregnated composite tape in response to heating; and

curing the resin after forming the braided preform into the braided radius filler.

4. The method of clause 1, wherein the braided radius filler has radius filler corners, the method further comprising the steps of:

adding an adhesive tip to at least one of the radius filler corners.

5. The method of clause 1, further comprising the steps of:

installing the braided radius fillers in a final forming die set;

applying at least one of heat and pressure to the braided radius filler in the final forming die set; and

the profile of the opposed radius filler side surfaces is formed to complement the profile of the radius filler region of the composite structure.

6. The method of clause 1, wherein the plurality of fibers comprise a resin, the shape of the woven preform approximates the shape of the woven radius filler, the step of shaping the woven preform comprising:

installing the braided preform in a mandrel forming system having a mandrel die and a mandrel forming base;

injecting a ceramic matrix into a mandrel mold cavity containing the braided preform;

allowing the ceramic matrix to harden into a hardened matrix;

heating the ceramic matrix in a manner that causes the ceramic matrix to expand; and

consolidating the woven preform in response to expansion of the ceramic matrix.

7. A method of manufacturing a composite structure, the method comprising the steps of:

installing a woven radius filler in a radius filler region between opposing reinforcement bullnose corners of a pair of back-to-back reinforcement laminates;

assembling a base laminate with the stiffener laminate to encapsulate the woven radius filler within the radius filler region and form a laminate assembly; and

curing the laminate assembly by applying heat to form a composite structure.

8. The method of clause 7, further comprising the steps of:

applying an adhesive layer to a surface of the opposed stiffener bullnose;

mounting the woven radius filler on the adhesive layer such that a radius filler side surface contacts the adhesive layer; and

covering a fillet bottom surface with the adhesive layer after placing the braided fillet filler in the fillet filler zone.

9. The method of clause 7, wherein:

the braided radius filler has a generally triangular cross-sectional shape including a radius filler bottom surface and an opposing radius filler side surface, the radius filler side surface being concave and formed complementary to an opposing stiffener bullnose of the stiffener laminate, the radius filler bottom surface being generally flat.

10. A method of manufacturing a radius filler, the method comprising the steps of:

providing a fillet filler core;

manufacturing a lining; and

covering the radius filler core with the bushing to form a bushed radius filler.

11. The method of clause 10, wherein the step of manufacturing the bushing comprises:

a plurality of fibers are woven into a woven liner.

12. The method of clause 10, wherein the steps of manufacturing a liner and covering the radius filler core comprise:

weaving fibers onto the radius filler core to form a woven liner covering the radius filler core.

13. The method of clause 10, wherein the step of manufacturing the bushing comprises:

assembling the liner from a woven fabric to form a woven liner.

14. The method of clause 10, wherein the step of manufacturing the bushing comprises:

manufacturing a legged bushing having at least one leg extending outwardly from a main bushing portion along a length of the bushing; and is

The legged bushing is configured such that the at least one leg intersects the main bushing portion at a fillet corner of the padded fillet of the bushing.

15. The method of clause 14, wherein the step of manufacturing the leg sleeve comprises:

stitching the at least one leg to the main liner portion along a length of the liner.

16. A method of manufacturing a composite structure, the method comprising the steps of:

installing a lined radius filler in a radius filler region between opposing reinforcement bullnose corners of a pair of back-to-back reinforcement laminates;

assembling a base laminate with the stiffener laminate to encapsulate the lined radius filler within the radius filler region to form a laminate assembly; and

curing the laminate assembly by applying heat to form a composite structure.

17. The method of clause 16, wherein:

the lined radius filler has a generally triangular cross-sectional shape and includes a liner covering a radius filler core, the liner being woven or assembled from a woven material; and is

The bushed radius filler has a radius filler bottom surface and opposing radius filler side surfaces that are concave and formed complementary to the opposing stiffener bullnose of the stiffener laminate, the radius filler bottom surface being substantially flat.

18. The method of clause 17, wherein:

the bushing is a legged bushing having legs extending outwardly from a main bushing portion along a length of the bushing, each leg intersecting the main bushing portion at a fillet corner of the padded fillet of the bushing.

19. A radius filler, comprising:

a plurality of fibers encapsulated in a resin and woven into a woven radius filler; and is

The braided radius fillers have a generally triangular shape with concave radius filler side surfaces and a generally flat radius filler bottom surface.

20. The radius filler of clause 19, further comprising:

an adhesive tip located on a fillet filler corner of the braided fillet filler.

21. The radius filler of clause 19, wherein:

the plurality of fibers have different offset angles at least two locations along the length of the radius filler; and is

The braided radius filler has different cross-sectional dimensions corresponding to the different offset angles at the at least two locations.

22. A radius filler, comprising:

a fillet filler core;

a bushing covering the radius filler core to form a radius filler with a bushing; and is

The lined radius filler has a rounded filler bottom surface that is concave and an opposing rounded filler side surface that is generally flat.

23. The radius filler of clause 22, wherein: the radius filler core is non-woven.

24. The radius filler of clause 22, wherein: the bushing is woven or assembled from a woven material.

25. The radius filler of clause 22, wherein:

the bushing is a legged bushing having at least one leg extending outwardly from a main bushing portion along a length of the bushing, the at least one leg intersecting the main bushing portion at a fillet corner of the padded fillet of the bushing.

26. The radius filler of clause 25, wherein:

the at least one leg is stitched to the main liner portion along a length of the liner at a location of the radius filler corner of the padded radius filler.

Additional modifications and improvements of the present disclosure may be apparent to those of ordinary skill in the art. Accordingly, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present disclosure and is not intended to serve as limitations of alternative embodiments or devices within the spirit and scope of the present disclosure.

Claims

1. A radius filler, comprising:

a plurality of fibers (308) encapsulated in a resin and woven into a woven radius filler (230); the braided radius filler has a generally triangular shape with concave radius filler side surfaces (232), a generally flat radius filler bottom surface (234), radius filler corners (236) where the radius filler side surfaces (232) meet each other, and radius filler corners (236) where each of the radius filler side surfaces (232) meets the radius filler bottom surface (234); and

an adhesive tip (244) on at least one of the radius filler corners (236), a remainder of the braided radius filler being free of adhesive.

2. The radius filler of claim 1, wherein:

the plurality of fibers have different offset angles at least two locations along the length of the radius filler.

3. The radius filler of claim 2, wherein:

4. The radius filler of claim 1, wherein:

the plurality of fibers (308) is braided onto the inner core (242).

5. A radius filler, comprising:

a rounded filler core (266);

a sleeve woven from a plurality of fibers and covering the radius filler core to form a radius filler (260) with a sleeve; the bushed radius filler has a generally flat radius filler bottom surface and opposing concave radius filler side surfaces (232) defining a braided main liner portion (272), the braided main liner portion (272) having three radius filler corners including a radius filler corner where the radius filler side surfaces meet each other and a radius filler corner where each of the radius filler side surfaces meets the radius filler bottom surface;

at least one braided leg (274) braided from a plurality of fibers and extending outwardly from one of said filleted filler corners of said braided main liner portion (272) and along a length of said main liner portion (272); and is

The at least one braided leg portion (274) and the main liner portion (272) are braided as a unitary structure.

6. The radius filler of claim 5, wherein:

the radius filler core is non-woven.